The present invention relates to a mounting structure of a head cover on a barrel-type apparatus used for a casing of a turbo machine or the like or a pressure vessel, to a vessel or a casing having the mounting structure, and also a centrifugal compressor housed in the casing.
As a structure to fix a head cover of a centrifugal compressor, a bolted structure as shown in FIG. 1 of JP Published Patent Application No. 55-125398 A (1980) is most frequently used. In the bolted structure, however, it is necessary to increase the number of bolts as the pressure inside a casing increases. Thus, there is a problem that assembling and disassembling operations become complicated and the bolted structure increases in cost.
To solve the problem, a shear key structure as shown in FIG. 5 of JP Examined Patent Application Publication No. 49-37932 B (1974) or the like is used in the high-pressure casing. In the structure, a shear key having a smaller inner diameter than that of a groove provided in a casing is mounted on the groove, and a head cover is thereby fixed to the casing. Some improvements of the shear key structure have been proposed.
According to FIG. 3 of JP Published Patent Application No. 55-125398 A (1980), a ring-shaped stopper for radially fixing the shear key is provided on the inner diameter side of the shear key, to thereby restrict the rotation of the shear key. Meanwhile, according to FIG. 6 of JP Published Patent Application No. 55-125398 A (1980), the shear key is provided with a shoulder, in addition to the ring-shaped stopper structure, and the outer diameter of the shoulder is brought into contact with the inner diameter of the casing, to thereby reduce a force applied to the shear key.
According to FIG. 1 of U.S. Pat. No. 3,934,752, the shear key is axially segmented into two members, with respect to the shear key structure shown in FIG. 5 of JP Examined Patent Application Publication No. 49-37932 B (1974). According to FIG. 3 of JP Examined Patent Application Publication No. 49-37932 B (1974), instead of a shoulder of the head cover in the structure shown in FIG. 1 of U.S. Pat. No. 3,934,752, the shear key is segmented into two members and its axially inner side member is provided with a shoulder. According to FIG. 1 of JP Published Patent Application No. 48-21804 A (1973), an axially outer side one of the shear key members segmented into two is also provided with a shoulder, the outer diameter of the shoulder is disposed in contact with the inner diameter of the casing, and the two shear keys are fixed by using bolts.